As new transportation means other than buses and railroads, track-based transportation systems in which a vehicle travels on a track using traveling wheels consisting of rubber tires, and guide wheels of the vehicle are guided by guide rails are known. Such track-based transportation systems are generally referred to as new transportation systems or automated people movers (APMs).
In the track-based transportation systems, there are some systems in which tires of a steering bogie can be steered so as to be capable of smoothly passing through a curved portion of the track when traveling on the curved portion of the track. A tire to be steered is generally a single tire in consideration of steering performance.
In this way, since the tire to be steered is the single tire, it is necessary to support the load of the vehicle with the single tire. For this reason, the weight of the vehicle is limited, and application of a steering carriage to a large-sized vehicle is difficult. Additionally, in order to maximize the imposed load while using the single tire, a technique of enclosing nitrogen gas so that the internal pressure is raised as high as possible is used. This becomes a factor of an increase in costs.
Additionally, in the single tire, the imposed load per tire becomes large. Thus, there is also limitation to maximum speed, and the single tire is generally used in a speed zone of 80 km/h or less.
Here, PTL 1 discloses that dual tires are used as steering wheels in a steering device to be applied to an automobile. In this steering device, a difference in rotation traveling distance between a tire outside a curve and a tire inside the curve is absorbed by using a differential gear. By applying the structure of the dual tires disclosed in PTL 1 to the tires steered by the steering bogie of the track-based transportation systems, it is possible to increase the imposed load of the tires.